1. Field of the Invention
The present invention relates to an endoscope image processing method and apparatus for observing fluorescence emitted from a subject when exposed to excitation light. The invention also relates to an endoscope system using the same.
2. Description of the Related Art
It is known that a living tissue emits self fluorescence when exposed to excitation light of a certain wavelength. Consequently, an endoscope apparatus that emits excitation light on a living tissue in a body cavity and observes self fluorescence emitted from the living tissue is proposed. Here, when observing the fluorescence, a fluorescence image that indicates the emission state of fluorescence and a background image that indicates the exposure state of excitation light are required in order to compare a region on which the excitation light is emitted and a region from which the fluorescence is emitted.
Here, it is known that excitation light reflected from the subject and the fluorescence are spectrally separated from each other by half prism, band-pass filter, or the like, and the excitation light and fluorescence are imaged by separate imaging devices. Further, a method in which a barrier filter that blocks excitation light and transmits fluorescence and a barrier filter that blocks the fluorescence and transmits the excitation light are switched at a constant period to obtain a fluorescence image of the fluorescence and a background image of the excitation light at different times is proposed as described, for example, in Japanese Unexamined Patent Publication No. 2000-270265.
Imaging of a fluorescence signal and a background signal by separate imaging devices poses a problem that it requires a plurality of imaging devices and other optical components, such as a half prism and the like, resulting in a complicated system configuration. Further, where a fluorescence image and a background image are obtained in a time-series manner as described in Japanese Unexamined Patent Publication No. 2000-270265, a difference in spatial position may occur between the background image and fluorescence image if the subject moves, thereby posing a problem that accurate diagnosis is prevented.
In view of the circumstances described above, it is an object of the present invention to provide an endoscope image processing method and apparatus, and an endoscope system capable of obtaining a fluorescence image and a background image with a simple system configuration.